Human cytomegalovirus (CMV) is the most common cause of non-hereditary sensorineural hearing loss in the U.S. Current therapies to treat infection during pregnancy or upon birth are unproven and risky. The experimental antiviral compound maribavir is a specific inhibitor of the CMV protein kinase, pUL97, and exhibits low toxicity. The objective of my proposal is to identify the molecular mechanism behind pUL97 kinase-mediated regulation of CMV gene expression and determine the impact of inhibiting kinase activity on CMV infected embryonic stem cell-derived neuronal progenitor cells. I have demonstrated that inhibition of the CMV kinase resulted in decreased expression of viral immediate early (IE) genes. This is a newly identified function of the CMV pUL97 kinase. Our lab previously identified an interaction between the CMV pUL97 kinase and cellular histone deacetylase 1 (HDAC1). HDAC1 acts as a repressor and is recruited to the MIE promoter at early times during infection. Therefore, I hypothesize that the kinase activity of CMV pUL97 influences the histone modification pattern at the viral major immediate early promoter by altering cellular HDAC1 activity. I propose to evaluate the pUL97-dependent changes of histone modifications at the major immediate early promoter (MIEP) during infection. These studies will be initiated using human diploid fibroblasts. In addition, I will identify pUL97-mediated changes in HDAC1 localization within the infected cells and at the MIEP. Other herpesvirus kinases phosphorylate HDAC1 and I propose several approaches to identify potential changes in HDAC1 phosphorylation by pUL97. I will determine the impact of these changes on HDAC1 deacetylase activity. I will further these studies using an embryonic stem cell-derived neural progenitor cell line (ES-NPCs) as a model system for CMV-induced neurological damage due to congenital CMV infection. Expression of IE genes has been demonstrated to alter fetal/neonate NPC differentiation. CMV IE genes regulate cell cycle and apoptosis in human diploid fibroblasts. I will test the role of pUL97 during these early events in the context of ES-NPC's by confirming the major results that were obtained in our fibroblast studies. I will determine the effectiveness of maribavir in preventing the pathogenic effects of HCMV infection on neuronal development. My studies will determine if a pUL97 kinase inhibitor is suitable for treating CMV infected neonates and possibly CMV infected mothers at risk of congenital infection.